Apparatus and methods currently used for carrying out patient fluid management require whole blood to be removed from the patient and processed in two ex-vivo stages. In a first stage the blood is processed to separate plasma, and in a second stage the plasma is processed in an ultrafiltration apparatus to remove plasma water and toxins. Although such procedure reduces the blood volume to normality, thereby treating fluid overload, the procedure causes massive change in blood hemodynamics in a short period of time including producing heavy stress on the human system with severe fluctuations and blood pressure and trauma to other body organs. Moreover, whole blood removal results in the necessity to heparinize or anticoagulate the patient to minimize clotting in the ex-vivo circuit and apparatus. Such treatment is counter-indicated in most surgical patients and deleterious to others due to consequential damage to blood components and the removal of vital blood components unrelated to the therapy. Removing and treating whole blood ex-vivo dictates that the procedure be a “batch” or intermittent process with attendant loss of efficiency and confinement of the patient to a clinical setting where support systems and machinery are available. Removal of whole blood also exposes the patient to contamination by viral and/or bacterial infection from nosocomial sources, and removal of erythrocytes, platelets and other large cellular blood components exposes them to risk of damage due to mechanical and chemical exposure to non-biocompatible surfaces of ex-vivo apparatus.